EP1276656A2

EP1276656A2 - Wheel supporting device and suspension device comprising same

Info

Publication number: EP1276656A2
Application number: EP01938047A
Authority: EP
Inventors: Loic Serra; Christian Tetaz
Original assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Current assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Priority date: 2000-03-27
Filing date: 2001-03-26
Publication date: 2003-01-22
Anticipated expiration: 2021-03-26
Also published as: WO2001072572A3; EP1276656B1; AU2001263811A1; DE60134131D1; US20030071430A1; US6688620B2; ATE396100T1; WO2001072572A2; JP2003528771A; WO2001072572A9

Abstract

The invention concerns a suspension device (1) comprising a wheel carrier (31) articulated relative to the suspension elements (18, 19). Said linkage is provided by rigid wishbones (6, 7). That additional degree of freedom enables to vary the camber ( alpha ) independently of the suspension travel and of deformations of its elements. Said camber variation is controlled, preferably, by the forces to which the wheel is subjected (2) in the contact zone (AC). This is obtained by the configuration provided wherein the movements of the wheel (2) relative to the vehicle body (5) allow an instantaneous rotation centre (CIR r/c) located beneath the ground plane (S).

Description

Wheel support device and suspension device comprising said support device

The present invention relates to the ground connection of vehicles, in particular the suspension devices, and more particularly the guidance of the wheels. Suspension devices have two main functions which must be carried out simultaneously at all times during operation. One of these functions is that of suspending the vehicle, that is to say allowing substantially vertical oscillations of each wheel as a function of the load applied to this wheel. The other of these functions is that of guiding the wheel, that is to say controlling the angular position of the wheel plane.

We call "wheel plane" the plane, linked to the wheel, which is perpendicular to the axis of the wheel and which passes through the center of the area of contact with the ground. The angular position of the wheel plane relative to the vehicle body is defined by two angles, the camber angle and the steering angle. The camber angle of a wheel is the angle separating, in a transverse plane perpendicular to the ground, the wheel plane from the median plane of the vehicle. This angle is positive when the upper part of the wheel deviates from the median plane towards the outside of the vehicle, we then commonly speak of "camber" or "positive camber". Conversely, when this angle is negative, we speak of "camber" or "negative camber. The steering angle of a wheel is the angle separating, in a horizontal plane parallel to the ground, the plane wheel of the median plane of the vehicle.

On most vehicles, the camber angle (we will use either camber or camber angle thereafter) is fixed for a particular position of the suspension and the steering, that is to say that it cannot theoretically not vary independently of the suspension travel or the steering. However, it undergoes variations induced by the deformations of the constituent elements of the suspension device caused by the forces exerted by the ground on the wheel. These variations can be significant. For example, a current passenger vehicle sees its camber vary by several degrees under the transverse forces developed on the tire in a curve, independently of the contribution of the roll of the vehicle body (which generally tilts in the same direction under the effect of centrifugal force). This “elastic” variation in the camber increases the camber (the camber tends towards positive values) for the wheel outside the turn. Conversely, the camber decreases (it tends towards negative values) for the inner wheel at the turn. We have been integrating these foreseeable variations in the design or adjustment compromises of the suspension devices of these current vehicles in order to limit the harmful effects they have on the functioning of the ground connection.

The camber has a great influence on the behavior of the vehicle and the performance of the ground connection. In particular, the performance of a tire varies widely depending on the configuration of its contact area on the ground and this configuration depends to a large extent on the camber. It is these variations that mainly motivate the choice of the static camber angle. Thus, for example, a large negative static camber is generally introduced on a competition vehicle in order to compensate for the variations due to the deformations of the tire under transverse force, suspension elements which are however much more rigid than on passenger vehicles and on the roll of the box. This configuration is both useful and acceptable in competition because the cornering grip criteria are predominant. On the contrary, on a passenger vehicle, the wear of the tires and the stability in a straight line having more weight in the desired compromise, one chooses an initial static camber very slightly negative and one accommodates reduced thrusts of drifts, when the deformations of the tire and of the elements of the connection to the ground under the lateral forces see their effects on the positioning of the wheel plane add to the effects of the roll of the vehicle.

In order to optimize the camber, in particular during transverse accelerations, suspension devices have been designed, the camber of which varies as a function of the vertical travel of the wheel. In this way, the roll taken by the vehicle body can induce a useful variation of the camber which partially or totally compensates for the inclination of the vehicle body and the deformations described above. This is the case of systems called "multi-arm". These devices require a specific vehicle design and architecture, which cannot, for reasons of space and cost, be implemented on most current vehicles. These systems react only to the consequence (travel, roll) of a transverse acceleration and not to the forces which cause it which on the one hand delays the effect of the correction. In addition, to allow a sufficient variation of the camber, the kinematics of these systems impose displacements of the position of the contact area with respect to the vehicle, called “lane variations” and these variations can also constitute a hindrance. The amplitude of the camber corrections made possible by such systems is therefore relatively limited when one wishes to respect the compromise necessary for the proper functioning of other load cases such as driving on bumpy roads, unilateral or on the contrary simultaneous pumping.

From a kinematic point of view, in terms of degrees of freedom, the suspension devices generally have only one degree of freedom (of the wheel or of the wheel carrier relative to the vehicle). This degree of freedom allows vertical suspension movements which, as we have just seen, can be combined with limited camber variations.

However, systems are known where the camber control is active, that is to say that the geometry modifications are controlled by movements of jacks, as described, for example, in documents US 4515390, US 4700972, and DE 19717418. In these systems, at least one additional degree of freedom has been allowed controlled by actuators. These systems are very specific since they cannot relate to the most common vehicles in particular because of their size and the large power required for the actuators.

An objective of the invention is a simple construction device, which allows a camber control without energy input or with a limited input, substantially independently of the vertical oscillations of the suspension and, more generally, of the movements of the vehicle body. , and which minimizes track variations.

This objective is achieved by a support device intended to link a wheel to the suspension elements of a vehicle, said wheel of radius 'R' being intended to rest on the ground, said support device comprising camber means conferring on said wheel with a degree of camber freedom with respect to said suspension elements, said support device being configured so that said wheel admits, around a medium position, a first instantaneous center of rotation situated in an interval ranging from 0.5 R above the ground to R below the ground. This support device in fact replaces the rigid wheel carrier of the prior art. The term “suspension elements” means the elements ensuring load recovery and conferring generally vertical travel on the wheel, such as arms, springs, shock absorbers or anti-roll links.

Preferably, said first instantaneous center of rotation is located below the ground plane. More preferably, said first instantaneous center of rotation is located transversely under said contact area.

According to one embodiment, the support device is configured so that it is close to equilibrium in said average position in the absence of transverse force exerted by the ground on the wheel in the contact area. This balance can be an unstable balance.

Preferably, said first instantaneous center of rotation is situated substantially in the plane of the wheel.

Preferably, the support device of the invention comprises a wheel carrier and it is intended to be linked to an intermediate support, said intermediate support constituting one of said suspension elements.

According to one embodiment, the wheel carrier is linked to the intermediate support by connecting rods configured so as to allow the camber movement of the wheel carrier by an instantaneous movement of rotation of the wheel carrier relative to the intermediate support.

According to another embodiment, said degree of camber freedom is imparted by elastic deformations of deformable elements linking the wheel carrier to said suspension elements.

The suspension elements may include a Macpherson strut.

The support device according to the invention may also include control means capable of influencing the camber of the wheel. These control means may include an elastically deformable element opposing the camber movement, this elastically deformable element preferably consisting of elastomeric joints.

The invention also relates to a suspension device for a vehicle comprising the support device described above.

This suspension device, which is intended to connect a wheel carrier to a body of a vehicle, said wheel carrier being intended to carry a wheel of radius 'R', said wheel being intended to rest on the ground by means of a contact area, includes means giving the wheel carrier, with respect to the body, a degree of camber freedom and a degree of freedom of suspension travel independent of each other, and it is configured so that the camber movement of the carrier wheel relative to the body admits, around an average position, a second instantaneous center of rotation located in an interval going from 0.5 R above the ground to R below the ground. The suspension device of the invention has two degrees of freedom allowing independent suspension and camber movements. The camber movement of the wheel (or of the wheel carrier) takes place around a second instantaneous center of rotation located at a limited distance from the contact area in order to limit track variations when taking camber or against camber and limit the energy input required in the case of active camber control.

In a preferred embodiment, said instantaneous center of rotation is situated in an interval ranging from 0.2 R above the ground to 0.4 R below the ground and preferably still, from 0.1 R above the ground to 0.3 R below the ground .

In order to ensure stable operation, the device is preferably configured so that it is close to equilibrium in said average position in the absence of transverse force exerted by the ground on the wheel in the contact area and preferably still, configured so that, in the absence of camber variations, the transverse force exerted by the ground on the wheel in the contact area generated during the suspension travel does not exceed not a limit corresponding to 0.3 P, "P" being the weight of the vehicle.

A preferred embodiment of the invention comprises an intermediate support linked on the one hand to the body and on the other hand to the wheel carrier, the connection of said intermediate support to the wheel carrier allowing said degree of camber freedom and the connection of said intermediate support to the body allowing said degree of freedom of suspension travel.

To allow passive operation, said second instantaneous center of rotation of the movement of the wheel carrier relative to the vehicle body may preferably be located below the ground plane so that transverse forces exerted by the ground on the wheel in the contact area induce an inclination of the wheel carrier relative to the body in the direction of a reduction in camber when said transverse forces are directed towards the interior of the vehicle and in the direction of an increase in camber when said transverse forces are directed towards the outside of the vehicle. In this case of passive operation linked to efforts transverse, the device may include a means of measuring the camber movement of the wheel carrier in order to deduce said transverse forces.

Under certain conditions, it may be necessary or advantageous to further provide control means capable of influencing the camber of the wheel. These means may include an elastically deformable element opposing the camber movement, the deformable element being constituted for example by elastomeric joints.

Preferably, said degree of camber freedom can be controlled by active means as a function of the running parameters of said vehicle.

Finally, the invention relates to a vehicle equipped with such a suspension device.

Several embodiments of the invention will be described in order to illustrate the characteristics and to set out the principles thereof. Of course, many other embodiments of the invention are possible as suggested by the many variations presented.

-Fig 1: Diagrams of principle and operation of a device according to the invention. -Fig 2: Diagram of a device according to a first embodiment of the invention in longitudinal view,

-Fig 3: Diagram of the device of Figure 2 in longitudinal view when subjected to a transverse force, -Fig 4: Diagram of a device according to a second embodiment of the invention, -Fig 5: Diagram d a device according to a third embodiment of the invention, -Fig 6: Diagram of a device according to a fourth embodiment of the invention, -Fig 7: Diagram of a device according to a fifth embodiment of the invention, -Fig 8: Diagram of a device according to a sixth embodiment of the invention, -Fig 9: Diagram of a device according to a seventh embodiment of the invention, -Fig 10: Diagram d 'a device according to an eighth embodiment of the invention.

Figure 1 shows in plan longitudinal view the principle of a suspension device according to the invention. This planar representation (that is to say in 2 dimensions) is very convenient because it clearly shows how the device according to the invention is distinguished from the devices of the prior art. The suspension device 1 comprises a wheel carrier 3 intended to maintain the plane PR of a wheel 2, relative to the body 5 of a vehicle. The wheel, of radius “R”, is in contact with the ground S via its contact area AC. The wheel carrier 3 is linked to the body 5 by means (4, 6, 7, 8, 9) allowing it two degrees of freedom. The camber movement of the wheel is allowed by a connection of the wheel carrier 3 with the intermediate support 4 by links 6 and 7. The movement of suspension travel is allowed by a connection of the intermediate support 4 with the body 5 by upper 8 and lower arms (or triangles) 9. Thus, the suspension device 1 is configured so as to give the wheel carrier, with respect to the body 5, a degree of camber freedom since the wheel carrier can 'tilt with respect to the body and a degree of freedom of suspension travel since the wheel carrier can perform substantially vertical movements in a manner known per se, for example in the manner of "multi-arm" or "double triangle" systems .

The movement of the wheel carrier 3 relative to the intermediate support 4 admits a first instantaneous center of rotation (CIR r / s). The movement of the wheel carrier relative to the body admits under transverse force a second instantaneous center of rotation (CIR r / c). The movement of the intermediate support 4 relative to the body 5 admits a third instantaneous center of rotation (CIR s / c). By applying the classic hypothesis of a point-like connection of the wheel 2 on the ground S, the theory of the collinearity of the instantaneous centers of rotation in a plane movement makes it possible to locate the second instantaneous center of rotation (CIR r / c) of the camber movement at the intersection of the wheel plane PR and the line (DC) carrying the first and third instantaneous centers of rotation. This kinematic theory is in common use in the field of ground bonding. It is then understood that it is the choice of configuration, that is to say of the dimensions and of the orientation of the various constituent elements of the suspension device which (by defining the positions of the characteristic axes) makes it possible to obtain a desired position the second instantaneous center of rotation (CIR r / c) of the camber movement of the wheel with respect to the body under transverse force. FIG. 1 represents the suspension device in a medium position, which could be defined as the position corresponding to driving in a straight line on flat ground, the vehicle carrying its rated load. The static camber is represented here by the angle α formed by the wheel plane PR with the plane PN passing through the center of the contact area and parallel to the median plane of the vehicle. This figure shows the kinematic operation of the device of the invention. The static balance of the forces undergone by the system (weight of the vehicle, forces of the ground on the wheel, suspension springs) must naturally be ensured by the design of the system. In In particular, the anchoring points and the thrust directions of the springs carrying the load are chosen for this purpose. It is also possible to add stiffnesses at the joints so as to control the angle of static camber by the position of the wheel carrier 3 relative to the intermediate support 4. These stiffnesses can be provided by elastic joints or by additional springs .

FIG. 2 represents an embodiment of the suspension device of the invention. In this example, the suspension movement movement is ensured by a MacPherson strut 18 and a lower arm or triangle 19. The pivot axis AP is the axis around which the strut pivots to allow the vehicle to be steered in a manner known per se. On this strut is articulated a wheel carrier 3 by links 6 and 7. The strut constitutes in this embodiment the intermediate support 4 of Figure 1. In addition, the first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier relative to this intermediate support 18 is located at the intersection of the axes of the rods 6 and 7, under the contact area AC, and substantially in the wheel plane PR which constitutes a preferred configuration. By virtue of the principle of collinearity stated above, the second instantaneous center of camber rotation (CIR r / c) is merged with the first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier relative to the intermediate support / strut 18. This configuration presents a perfectly stable equilibrium, that is to say that even in the absence of stiffness at the level of the articulations of the rods (as is the case for ball joints or mechanical axes), the device is in equilibrium in its average position in the absence of transverse force exerted by the ground (S) on the wheel in the contact area (AC). In practice, taking into account the various deformable elements such as the tire, a configuration close to theoretical equilibrium may be satisfactory in terms of operation. Experiments have shown that when the position of the first instantaneous center of rotation (CIR r / s) t> ar stiffener at the center of the wheel forms a lower anσlp.πr at 1 °

decreases, it tends towards negative values). Naturally, when the wheel is subjected to a force whose transverse component is oriented towards the outside of the vehicle (this is the case of the wheel which is on the inner side at a curved trajectory) the component Fy generates a torque which tends to rotate the wheel carrier in the direction of an increase in camber (that is to say that the camber angle αl increases, it tends towards positive values). The first instantaneous center of rotation (CIR r / s) being the point of intersection of the axes of the rods (6, 7) which define the kinematics of the movements of the wheel carrier 3 relative to the strut 18, the position of this point is variable during the camber movements of the wheel carrier as can be seen by comparing Figures 2 and 3. However, we also note that the position of the second instantaneous center of rotation (CIR r / c) of the camber movement of the door -wheel 3 compared to the body 5 of the vehicle varies less. This slight variation in the position of the second instantaneous center of rotation (CIR r / c) during camber movements can be used to gradually vary the torque generated by the transverse forces in the contact area. In the example of FIG. 3, this effect stabilizes the system, because the torque which generates the camber tends to decrease when the camber deviates from its average value due to the decrease in the distance between the second instantaneous center of rotation (CIR r / c) and the ground, which constitutes the lever arm to which the transverse force Fy applies.

FIG. 3 represents, for convenience, the variation in camber of the wheel generated by a transverse force Fy in the case of an "ideal" vehicle, that is to say perfectly rigid. In reality, on most current vehicles, a transverse force also generates a roll (that is to say an inclination of the reference plane PV) of the body towards the outside of a turn which tends to incline the plane of wheel out of the bend (read above). In this case, these two effects are inverse. Thus, the variation illustrated in FIG. 3 is to be considered relative to the body, that is to say the plane PV linked to the body. To know the position of the wheel relative to the ground, it is naturally necessary to integrate the variation induced by the roll (and also by the deformations of the various elements of the connection to the ground).

Figure 4 shows a different configuration from Figure 2 but uses similar elements. The difference lies in the fact that the wheel carrier 31 being located under the points of connection to the strut 18, the links 6 and 7 work in compression. Thus, the balance of the wheel carrier is an unstable equilibrium while it is stable in the case of FIG. 2. An advantage of this instability is that it can make it possible to obtain greater sensitivity around the mean position. . In order to allow direct comparison with others Figures, the instantaneous centers of rotation (CIR r / s, CIR s / c, CIR r / c) have the same positions (in the middle position of the wheel). However, this, as for the first mode, is only an example, an infinity of configurations being possible as described in Figure 1.

FIG. 5 shows an architecture close to that of FIG. 1. In fact, the degree of freedom of suspension movement is provided here by a “multi-arm” or “double triangle” system known per se. In this example, the arms 81 and 91 being mutually parallel and horizontal, the straight line DC carrying the instantaneous centers of rotation is also horizontal. This device differs from that of FIG. 1 in that, according to a preferred embodiment similar to that of FIGS. 2 and 3, the first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier 32 relative to to the intermediate support 41 is positioned substantially in the wheel plane PR, for an average position of the wheel 2 in terms of camber. Thus, this point also constitutes the second instantaneous center of rotation (CIR r / c) of the camber movement of the wheel carrier relative to the body. There is also shown in dotted lines, a control means 50, active or passive, in the form of a cylinder capable of imposing or limiting the camber variations. In the case of an active control, the position of the second instantaneous center of rotation (CIR r / c) of the camber movement is advantageously located at ground level S or above this level but at a reduced distance to allow control at low energy and limit the track variation caused by the movements of the wheel plane.

On the contrary, the control means can have a passive role of regulating the camber movements caused for example by transverse forces as shown in FIG. 3.

Whether passive or active, the control means, if it is controllable, can be controlled as a function of various vehicle running parameters (for example, longitudinal or transverse acceleration, steering wheel position, body roll, yaw sensor , forces on the wheels, type of driving, behavior desired by the driver).

According to a similar construction, the control means can be replaced by a means of measuring camber movements. In the case of camber movements caused by transverse forces, this measurement makes it possible, by methods known per se, to know these forces. The advantage of such a measurement system is that it is based on a large displacement, without common measurement with the displacements measured for example by strain gauges which are sometimes installed on the suspension elements. This knowledge of transverse efforts is useful, for example, for piloting safety systems or regulating the behavior of the vehicle.

FIG. 6 represents a device comparable to that of FIG. 5 in terms of kinematics but different in terms of stability of equilibrium as has been described for FIG. 4. The links 6 and 7 work here in compression between the door wheel 31 and the intermediate support 42. The suspension spring 60 is shown bearing on the intermediate support 42 but it can naturally bear on the wheel carrier 31 or on one of the upper arms 81 or lower 91 as in known suspension systems.

Figures 7 and 8 show alternative embodiments of the invention.

The device of FIG. 7 comprises a wheel carrier 33 linked by deformable elements 25, 26, 27, 28 to the strut 18 which here constitutes the intermediate support. These deformable elements are here elastomeric joints. The specific distribution of the radial stiffnesses of these articulations according to the azimuth makes it possible (if one considers small displacements) to create a connection of type “slide” according to the preferential axes of deformation (APD1, APD2, APD3, APD4). The arrangement of the joints 25, 26, 27, 28, and therefore of these “slide” connections, gives the wheel carrier 33 the kinematics sought with respect to the suspension elements as well as the stiffness and the functions of stops useful for controlling the device. . The first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier relative to the strut 18 is located at the intersection of the normal to the preferential axes of deformation (APD1, APD2, APD3, APD4). This configuration generates a sufficient camber amplitude for most applications and participates in the filtering of the vehicle suspension. In the example illustrated here, the specific distribution of radial stiffnesses is obtained by the presence of cells along the preferential axes of deformation in the elastomeric sleeves of the joints 25, 26, 27, 28 but those skilled in the art of elastomeric joints knows different solutions depending on the specifications of such joints. The second instantaneous center of rotation (CIR r / c) of the movement of the wheel carrier relative to the vehicle body is, in this position, coincident with the first instantaneous center of rotation (CIR r / s) as shown in the figure 2.

Four elastomeric joints have been shown here, but this number is arbitrary since two could be sufficient. On the other hand, the connection of the wheel (or of the wheel carrier) to the strut must also ensure the guiding of the wheel plane when turning. We can, for example to give good turning rigidity, use a wheel carrier consisting of two parallel and distant planes, located on either side of the strut, each of these two planes having the characteristics described in FIG. 7.

FIG. 8 represents an architecture close to that of FIG. 2. However, these are deformable parts 35, 36 which, by their own flexibility and not by a pivoting connection, provide the desired degree of camber freedom. Two flexible parts have been shown here, but this number is arbitrary. The connections between these deformable parts (35, 36), the wheel carrier 34 and the strut 18, are rigid. An advantage of this solution is that it eliminates the joints necessary for the operation of the embodiments of FIGS. 2 to 6. The deformable parts (35, 36) can be made of metal or of composite material. It is also possible to produce these deformable parts (35, 36), the wheel carrier 34 and the means of connection to the suspension 5 in a single piece and obtain the desired kinematics by an adequate distribution of the rigidities within this single part. In this case, the use of a composite can be advantageous. In this example, there is shown a first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier 34 relative to the intermediate support / strut 18 located approximately 0.75 R under the ground S. This configuration makes the system more sensitive to the transverse forces undergone by the wheel in the contact area. The second instantaneous center of rotation (CIR r / c) of the movement of the wheel carrier relative to the vehicle body is, in this position, coincident with the first instantaneous center of rotation (CIR r / s) as shown in the figure 2.

FIG. 9 represents the case of a rigid (or broken) axle as found on certain passenger vehicles and a majority of commercial vehicles. The rigid axle 20 here constitutes the intermediate support and its connection (not shown) to the vehicle body provides the movement of suspension travel. The wheel carrier 44 is, according to the invention, connected by two links 6, 1 to the rigid axle 20, so as to define a first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier relative to at Pessieu / intermediate support slightly above the ground S. The second instantaneous center of rotation (CIR r / c) of the movement of the wheel carrier relative to the vehicle body is, in this position, confused with the first instantaneous center of rotation (CIR r / s) of the movement of the wheel carrier relative to the axle because the latter is located in the wheel plane. A cylinder 30 makes it possible to actively control the movements of the wheel carrier relative to the suspension. This cylinder 30 can be controlled as a function of vehicle running parameters. Naturally, this alternative is not limited to the case of FIG. 9 but can be adapted to other embodiments. FIG. 10 represents an embodiment of the invention in which the wheel carrier 54 is articulated by links (6, 7) to the lower arm or triangle 92 of a “multi-arm” or “double-” suspension system triangle ". the upper arm or triangle 82, which supports the spring 61, is articulated by an additional link 55. This additional link 55 is oriented towards the first instantaneous center of rotation (CIR r / s) to have a neutral effect on the camber (in the average position of the wheel). The second instantaneous center of rotation (CIR r / c) of the movement of the wheel carrier relative to the vehicle body is, in this position, coincident with the first instantaneous center of rotation (CIR r / s) as shown in the figure 2.

As we have seen, we can choose, depending on the desired operation, a position of the second instantaneous center of rotation of the camber movement (CIR r / c) in an interval ranging from 0.5 R above the ground to R below the ground (R being the radius of the wheel). Positioning this point close to the ground limits the lane variation. For example, in the case of an instantaneous center of rotation located at R of the ground and for a wheel with a radius of 300 mm, a camber of 5 ° causes an offset of the contact area relative to the body (variation of half track) of about 25 mm. It was found that this value should be considered as a limit not to be exceeded. However, when the second instantaneous center of rotation of the camber movement (CIR r / c) is located above the ground, that is to say that the device of the invention must include an actuator in order to actively orient the plane of wheel (see Figure 5 and 9), experiments have shown that beyond a certain height, the power necessary for this active operation makes the system too complex and above all too energy consuming. This limit height has been found to correspond substantially to a half wheel radius.

In the case of passive operation as described above, one way of verifying the operation of the device of the invention (and of measuring its sensitivity) is to exert a transverse force (using, for example, a ball plate) at the contact area of the wheel of a vehicle fitted with the device of the invention and to measure the variation in the camber angle.

The different examples of the figures illustrate the fact that the suspension device of the invention can be produced from very different suspension principles, provided that the desired kinematic definition is obtained. In particular, the elements that we have represented in arbitrary forms can take any suitable form making it possible to adequately position the axes of articulation and naturally to withstand the stresses of the connection to the ground. Similarly, the figures represent cases where the articulation of the wheel carrier with respect to the intermediate support is a "virtual" articulation around the second instantaneous center of rotation (CIR r / s), that is to say that it n 'is not materialized by a mechanical axis but it results from the articulation of several elements. The fact that this articulation is virtual makes it possible to position the center of this rotation at any point of the plane and in particular close to the ground or even under the ground. A mechanical articulation, that is to say “non-virtual” like an axis can however be used when the position of the second instantaneous center of rotation (CIR r / s) is compatible in terms of size and ground clearance.

An interesting feature of the invention is that it is applicable to all known suspension schemes since additional elements are added to these existing systems allowing a degree of freedom of camber in addition to the degree of freedom of existing suspension. An advantage of this support or suspension device is its compactness which makes it possible not to question the design of current vehicles. One of the essential characteristics of the invention is that it allows a variation in the camber of each wheel independently of the other wheels of the vehicle and regardless of whether the wheel is driving or steering.

The figures represent in projection on a plane orthogonal to the ground and transverse to the vehicle passing through the point of application of the resultant of the forces in the contact area, the principles and several embodiments of the invention. This two-dimensional representation is advantageous in order to clearly illustrate the essential characteristics of the invention, the objective of which is a controlled variation of the camber. In this representation, the camber movement is a rotation in the plane around a pivot point (instantaneous center of rotation). However, it should not be forgotten that a rotation takes place in reality (in three dimensions) around a pivot axis, real or virtual (instantaneous axis of rotation). This axis is represented by a point in the planar representation. This axis can be constructed substantially parallel to the ground plane and to the longitudinal axis of the vehicle to allow the intended camber variations. However, by varying the orientation of this axis, it is possible to create, in addition to the cambering effects, additional turning, gripping, opening or winding effects as a function of the transverse (curved) and longitudinal ( braking, acceleration) suffered by the wheel in the contact area. A person skilled in the art knows, by carrying out tests and / or by theoretical methods, determining the orientation which should be adopted as a function of the behavior which he expects from this device. Experiments have example shown that a 6 ° inclination of this camber pivot axis with respect to the horizontal makes it possible to induce a deflection linked to the camber, at an angle 10 times less than that of the camber. So when the transverse forces induce a camber of 5 °, the steering is around 0.5 °. The inclination of the pivot axis can be obtained for example by equipping the vehicle with a device whose operating plane is inclined by 6 ° relative to the vertical.

The articulations of the various elements of the support device or of the suspension device of the invention can be produced in various ways. The elastomeric joints commonly used in the field of connection to the ground can make it possible to simplify the obtaining of the balance of the system because they introduce determined stiffnesses. On the other hand, it is known that they promote the comfort of the vehicle.

The support device or the suspension device of the invention can be implemented in order to compensate for the deformations of the elements of the ground connection of current vehicles and allow better performance. That is to say that the support device or the suspension device of the invention can be used to guarantee that the wheel plane remains, in all circumstances, substantially orthogonal to the ground plane or slightly inclined to also take into account possible deformation of the tire. This object is achieved by a device whose useful camber amplitude is only a few degrees. However, the support device or the suspension device of the invention can also be implemented with the aim of allowing a much greater variation in the camber, that is to say allowing an operation of the connection to the ground closer to that of a motorcycle than that of vehicles with three wheels and more, currently on the market.

In general, the figures represent a wheel 2 comprising a pneumatic tire, but the invention is naturally intended for any type of wheel with or without an elastic tire, pneumatic or non-pneumatic, an essential characteristic being the position of the instantaneous center of rotation with respect to the contact area, whatever it is.

Claims

claims

1. Support device (3, 6, 7) intended to link a wheel (2) to suspension elements (4, 8, 9) of a vehicle, said wheel (2) of radius 'R' being intended to rest on the ground (S), said support device comprising camber means (6, 7) giving said wheel a degree of camber freedom with respect to said suspension elements (4, 8, 9), said support device being characterized in that it is configured so that said wheel (2) admits, around a mean position, a first instantaneous center of rotation (CIR r / s) situated in an interval going from 0.5 R above from the ground to R below the ground.

2. Support device (3, 6, 7) according to claim 1, said first instantaneous center of rotation (CIR r / s) being located, for an average position of the wheel, below the ground plane (S).

3. Support device according to claim 2, configured so that said first instantaneous center of rotation (CIR r / s) is located transversely under said contact area (AC).

4. Support device according to one of the preceding claims, configured so that it is close to equilibrium in said average position in the absence of transverse force (Fy) exerted by the ground (S) on the wheel (2) in the contact area (AC).

5. Support device according to claim 4, configured so that said equilibrium is an unstable equilibrium.

6. Support device according to one of the preceding claims, said first instantaneous center of rotation (CIR r / s) being located substantially in the plane of the wheel (PR).

7. Support device according to one of the preceding claims, comprising a wheel carrier (3) and being intended to be connected to an intermediate support (4), said intermediate support constituting one of said suspension elements (4, 8 , 9).

8. Support device according to claim 7, the wheel carrier (3) being connected to the intermediate support (4) by links (6, 7) configured so as to allow movement camber of the wheel carrier by an instantaneous movement of rotation of the wheel carrier relative to the intermediate support (4).

9. Support device according to one of claims 6 or 7, characterized in that said degree of camber freedom is imparted by elastic deformations of deformable elements (25, 26, 27, 28) connecting the wheel carrier ( 33) to said suspension elements (18).

10. Support device according to one of the preceding claims, said suspension elements comprising a strut (18) of a Macpherson suspension system.

11. Support device according to one of the preceding claims, further comprising control means (30, 50) capable of influencing the camber of the wheel.

12. Support device according to claim 11, the control means comprising an elastically deformable element opposing the camber movement.

13. Support device according to claim 12, the elastically deformable element being constituted by elastomeric joints.

14. Suspension device (1) for a vehicle comprising the support device according to one of the preceding claims.

15. Suspension device (1) according to claim 14 intended to connect a wheel carrier (3) to a body (5) of a vehicle, said wheel carrier being intended to carry a wheel (2) of radius' R ', said wheel being intended to rest on the ground (S) by means of a contact area

(AC), said suspension device comprising means (4, 6, 7, 8, 9) giving the wheel carrier, relative to the body, a degree of freedom of camber and a degree of freedom of suspension suspension travel one from the other, said device being configured so that the camber movement of the wheel carrier relative to the body admits, around a medium position, a second instantaneous center of rotation (CIR r / c ) located in a range from 0.5 R above the ground to R below the ground.

16. A suspension device (1) according to claim 15, said second instantaneous center of rotation (CIR r / c) being located in a range from 0.2 R above the ground to 0.4 R below the ground.

17. Suspension device (1) according to one of claims 14 to 16, comprising an intermediate support (4) linked on the one hand to the wheel carrier (3) and intended to be connected on the other hand to the body ( 5), the connection of the wheel carrier to the intermediate support allowing said degree of camber freedom and the connection of said intermediate support to the body allowing said degree of freedom of suspension travel.

18. Suspension device (1) according to one of claims 14 to 17, said second instantaneous center of rotation (CIR r / c) of the camber movement of the wheel carrier (3) relative to the body (5) being located under the ground plane (S) so that transverse forces (Fy) exerted by the ground on the wheel (2) in the contact area (AC) induce an inclination of the wheel carrier (3) relative to the body in the direction of a reduction in camber when said transverse forces are directed towards the interior of the vehicle and in the direction of an increase in camber when said transverse forces are directed towards the outside of the vehicle.

19. Suspension device (1) according to one of claims 14 to 18, characterized in that said degree of camber freedom is controlled by active means as a function of rolling parameters of said vehicle.

20. Vehicle equipped with a suspension device (1) according to one of claims 14 to 19.